Channel letters are used to provide signage for buildings, shopping malls, and the like where it is desirable that the signage comprise illuminated letters or any other shapes that are easily seen, even at great distances, day or night. Each channel letter consists of an enclosure, usually a metal box, having a rear surface which is positioned against a raceway, or the wall of a building, on which the signage is mounted and a plurality of sides which define the figuration of a letter or number (or other shape) which make up a portion of the sign. A light source, such as a neon tube, LEDs, or other lighting mechanisms, can be positioned within the walls of the enclosure and attached to the rear (and/or side) surface to provide illumination for the letter or shape.
The light sources used in many existing channel letters are neon bulbs requiring high voltage power with transformers built into the metal enclosures. To prevent injury to those servicing such channels letters many municipalities require that such letters be inspected to ensure that they are adequately sealed using standards set by Underwriters Laboratories.
It is expected that relatively new technology in lighting sources will soon become the most prevalent for the manufacturers of channel letters. Specifically, low voltage LED type light sources have been developed which provide a very long lasting bright light without requiring the high voltage and transformers needed for neon lighting. It is expected that channel letters employing the new technology will not be required to meet the same standards set by Underwriters Laboratories for neon tubes.
In addition to the lighting, a channel letter also includes a planar transparent lens, the outer shape of which corresponds to the figuration of the letter or any other shape defined by the sides of the enclosure. The manufacture of the lens requires that the planar panel of transparent plastic be cut to the shape of the enclosure. The lens of existing channel letters have a trim cap glued or welded to the outer edges thereof which form a border to the lens. The trim cap also has a lip which, when assembled to the enclosure, is shaped to fit snugly around the forward ends of the walls thereof for retaining the lens to the enclosure and to maintain the water tight seal required by Underwriters Laboratories. Heretofore, typically screws are threaded through the lips of the trim cap and into the enclosure walls to retain the lens across the forward opening of the enclosure.
It would be desirable to provide a channel letter assembly having a lens and trim cap which could be installed without incurring the labor intensive, and aesthetically displeasing, step of attaching the trim cap with screws. It would also be desirable to provide a less cumbersome method of disassembling the trim cap and lens to gain access to the interior of the enclosure of a channel letter.